Gay rights activists are celebrating the 50th anniversary of the landmark "sip-in" at Greenwich Village's Julius' Bar.

It was back on April 21, 1966, when three members of the gay rights group the Mattachine Society went to the bar for a drink hoping to spark a movement.

One of the men was refused service after announcing he was gay.

They brought along a few newspaper reporters to cover the event, and publicity from the incident spurred a series of lawsuits that overturned laws that discriminated against gay people.

Civil rights activists say gay rights have come a long way.

"Fifty years is more like 50 light years because now, we have gay marriage and politicians who routinely mention LGBT rights," said Randolfe Wicker of the Mattachine Society.

"Three years and two months after the sip-in, we had Stonewall, and then everybody was empowered, but this was the opening salvo for the gay liberation movement in New York City," said Tom Bernardin, Julius' Bar historian.

In 1969, police raided a nearby bar, The Stonewall Inn, but patrons fought back, propelling the gay rights movement into the national spotlight.